Many modern portable devices (e.g., laptop computers, mobile phones, digital cameras, video cameras, media players, personal digital assistants (PDAs), game console, etc.) include battery packs. One particular type of conventional battery pack includes one or more battery cells coupled to one or more Integrated Circuit (IC) chips. The chips typically include a controller (e.g., a microcontroller) and circuitry and provide, among other things, battery cell management and protection.
Some conventional battery packs include a Li-ion (Lithium ion) battery cell, which is essentially a volatile chemical reaction packaged inside a cylinder. Potential energy is stored in each cell, and if the battery cell is exposed to conditions outside of its specification the cell can over heat, catch fire or explode. Conventional battery packs configured with these volatile cells typically include fail-safe circuitry for detecting unsafe conditions (e.g., charge or discharge over-currents, short circuits, etc.), and for taking corrective action to prevent damage to the battery cell and/or device, and to protect the end user.
In some conventional battery packs, two external transistors (e.g., field effect transistor (FETs)) are connected in series with the battery cell(s) and are enabled and disabled to allow for the charge and discharge of the cells. The transistors allow the cell(s) to be disconnected from either the charger or a device based on one or more monitored conditions to avoid improper or dangerous operation. The disabling of the FETs can be triggered by certain events, such as short-circuit, too deep of a discharge, or incorrect battery charging as a result of the detection of too high of currents for too long a time period, too high or too low battery cell voltages or too high temperatures. The enabling of the FETs is also triggered by certain other events, when it is considered that potentially dangerous conditions are not present or have been resolved.
In one configuration, referred to as a high-side solution, the two transistors are coupled in series between the positive terminal of the cell(s) and a positive battery pack terminal (e.g., the external positive terminal interface to a device). In a low-side solution, the two transistors are coupled in series between the negative terminal of the cell(s) and a negative battery pack terminal (e.g., the external negative terminal interface to a device).